title: Antibody-mediated platelet phagocytosis by human macrophages is inhibited by siRNA specific for sequences in the SH2 tyrosine kinase, Syk.
abstract: Immune thrombocytopenia depends upon Fc receptor-mediated phagocytosis that involves signaling through the SH2 tyrosine kinase, Syk. We designed small interfering (siRNA) sequences complementary to Syk coding regions to decrease the expression of Syk in the human macrophage cell line, THP-1. To evaluate the functional effect of siRNA on phagocytosis, we developed a new in vitro assay for antibody-mediated platelet ingestion by THP-1 cells. Incubation of THP-1 cells at 37°C with fluorescence-labeled platelets and anti-platelet antibody promoted ingestion of platelets that could be quantitated by flow cytometry. Transfection of THP-1 cells with Syk-specific siRNA resulted in a reduction in the amount of FcγRII-associated Syk protein. Coincident with decreased Syk expression, we observed inhibition of antibody-mediated platelet ingestion. These results confirm a key role for Syk in antibody-mediated phagocytosis and suggest Syk-specific siRNA as a possible therapeutic candidate for immune thrombocytopenia.
authors.affiliation: Department of Surgery, Shanghai East Hospital, Tongji University School of Medicine, 150 Jimo Road, Pudong New District, Shanghai 200120, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Lu
authors.forename: Weiming
authors.initials: W
authors.lastname: Wang
authors.forename: Huiming
authors.initials: H
authors.lastname: Mao
authors.forename: Hai
authors.initials: H
authors.lastname: Hu
authors.forename: Yanling
authors.initials: Y
authors.lastname: Wu
authors.forename: Bing-Guan
authors.initials: BG
authors.lastname: Chen
authors.forename: Zhongmin
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000906:Antibodies / Q000276:immunology; D001681:Biological Assay / Q000379:methods; D001792:Blood Platelets / Q000166:cytology / Q000276:immunology; D002460:Cell Line; D015536:Down-Regulation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology*; D010587:Phagocytosis / Q000187:drug effects*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000503:physiopathology; D034741:RNA, Small Interfering / Q000494:pharmacology*; D000072377:Syk Kinase
chemical_list: D000906:Antibodies; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase